Low car diet
Join Date: Aug 2007
Location: Corvallis, OR, USA
Posts: 2,407
Bikes: 2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Each crank has a specified BB spindle to achieve the correct chainline. E.g., two road triples will specify the same chainline but may use totally different spindle lengths depending on the shape of the crank arms.
Therefore, you can't just keep the original road BB and mate it to a new MTB triple and assume you'll have a road chainline.
You need to look up what BB spindle length is specified for the new crank (as well as what chainline that would achieve). Then, you can use a shorter spindle to achieve a narrower chainline. You'd shorten the spindle by double the amount of chainline you're trying to lose (e.g., 8mm shorter spindle to bring the chainline from 47.5mm to 43.5mm). But, you have to make sure the cranks won't hit the frame.